This invention relates to a marking tool assembly adapted for use with a punch press and adapted to stamp identifying indicia on a workpiece which is processed by the punch press. For example, the marking tool assembly may be used to stamp a part number into the workpiece.
In one type of punch press, a punch is carried on the lower end of a hydraulically actuated ram which is adapted not only to be reciprocated upwardly and downwardly but also to be rotated about a vertical axis. During the downstroke of the ram, the punch coacts with an underlying die to form a hole through the workpiece. By rotating the ram, a non-circular punch may be positioned to form a non-circular hole in a preselected angular orientation in the workpiece.
As the punch moves through its downstroke, a stripper ring moves downwardly into engagement with the workpiece to clamp the workpiece against the die during the punching operation. The punch then moves downwardly through the stripper ring and punches the hole. As the punch is retracted, the stripper ring holds the workpiece downwardly to enable the punch to strip out of the workpiece. Thereafter, the stripper ring is retracted upwardly to permit the workpiece to be repositioned beneath the punch.
Conventionally, the hydraulic actuator for the ram may be preset to effect automatic retraction of the ram when a predetermined downward force is exerted on the punch. As a result, the actuator is protected against overload.